#include<iostream>
#include<string>
using namespace std;
const int N = 1e5 + 10;
char s[N];
char ret[N];
int cnt[26] = { 0 };

int main()
{
    int n = 0;
    cin >> n >> s;
    char maxChar = 0;
    int maxCount = 0;
    for (int i = 0; i < n; i++)
    {
        int index = s[i] - 'a';
        if (++cnt[index] > maxCount)
        {
            maxChar = s[i];
            maxCount = cnt[index];
        }
    }
    if (maxCount > (n + 1) / 2)
    {
        cout << "no" << endl;
    }
    else
    {
        cout << "yes" << endl;
        int i = 0;
        while (maxCount)
        {
            //cout<<"maxCount:"<<maxCount<<endl;
            ret[i] = maxChar;
            //cout<<ret[i]<<endl;
            //cout<<"maxChar:"<<maxChar<<endl;
            i += 2;
            maxCount--;
        }
        //cout<<ret[2]<<endl;
        for (int j = 0; j < 26; j++)
        {
            if (cnt[j] && j + 'a' != maxChar)
            {
                while (cnt[j]--)
                {
                    if (i >= n) i = 1;
                    ret[i] = j + 'a';
                    i += 2;
                }
            }
        }
        for (int j = 0; j < n; j++)
            cout << ret[j];
    }
    return 0;
}